Internal combustion engines



J. SWAINE July 12, 1966 lNTERNAL COMBUSTION ENGINES 2 Sheets-Sheet 1 Filed April 1e, 1964 mit .$55k w J. SWAINE July 12, 1966 INTERNAL COMBUSTI ON ENGINES 2, ileetn-Shect 2 Filed April 16, 1964 United States Patent O 3,260,250 INTERNAL CGMBUSTION ENGINES John Swaine, Coventry, England, assignor to The Rover Company Limited, Solihull, England, a British com- This invention relates to improvements in internal combustion engines of the kind employing a carburetter and in particular concerns a method of reducing the amount of atmospheric pollution caused by such engines. Recent observations indicate that approximately twentyfive percent of air pollution caused by internalcombustion engines arises from crankcase fumes escaping to atmosphere through the crankcase breather.

To eliminate this source of atmospheric pollution it has been proposed to blank olf the crankcase breather and to connect the crankcase by means of a pipe to one or other of a number of possible points in the induction system of the engine so that the depression in the induction system would draw the fumes into the cylinders of the engine to be consumed. One such proposal has been to connect a pipe from the crankcase to the air cleaner that is usually provided at the inlet to the induction system; the depression here is only small and is often insucient for the purpose of reliably drawing in the fumes from the crankcase. This arrangement is moreover unsatisfactory since it produces undesirable deposits of carbonaceous material and moisture in the air cleaner and in the carburetter.

It has also been proposed to connect a pipe from the crankcase to a point in the induction manifold between the carburetter and the throttle valve, but the serious drawback here is that the depression varies very widely in the induction manifold and when the throttle valve is closed or nearly closed' at high engine speeds the large depression that is present in the manifold would be communciated to the crankcase, with obviously undesirable results. It is therefore necessary with this arrangement to incorporate some form of vacuum-limiting valve in the pipe.

According to the invention it is now proposed to overcome these drawbacks of the known arrangement by providing, in an internal-combustion engine aspirated through a carburetter of the so-called constant-vacuum or constant-depression type and through a throttle valve, to connect a pipe from the crankcase of the engine to a point in the induction system between the venturi of the carburetter and the throttle valve.

The characteristic of this type of carburetter is that a movable air valve member is actuated by a piston or diaphragm that responds to the pressure prevailing irnmediately downstream of the venturi in such a manner as to keep that pressure substantially constant. When the throttle valve is wide open, producing little or no pressure drop, then the air valve is likewise open and the depression is small. But when the throttle valve is closed or nearly closed, producing a large depression in the induction manifold, the pressure drop is chiefly across the throttle valve itself and so the depression between the carburetter air valve and the throttle valve is still small.

Accordingly we eliminate the necessity to t a vacuumlimiting valve in the pipe from the crankcase. Furthermore, since the crankcase fumes are introduced into the induction system downstream of the venturi there is no contamination of the fuel-metering section of the carburetter by deposits from the fumes.

The invention will now be further described by way 3,260,259 Patented July 12, 1966 icc of example with reference to the accompanying drawings, in which,

FIGURE 1 is a plan view of an engine to which the invention is applied;

FIGURE 2 is a plan view of the carburetter of the engine of FIGURE l;

FIGURE 3 is a partly sectioned side view of the carburetter; y

FIGURE 4 is a scrap section on the line 4-4 in FIG- URE 2; and

FIGURE 5 is a scrap horizontal section through a portion of the front wall of the crankcase of the engine, showing the crankcase end of the pipe.

The engine illustrated in FIGURE 1 is a four-cylinder in-line engine with its cylinders upright. Its induction manifold 1 receives a fuel-air mixture from a carburetter 2 which receives its air through an induction pipe 3 and air cleaner 4. A breather pipe S connects a llame trap 6 on the valve cover 7 of the engine to the air cleaner 4.

From a point low down on the front wall of a lateral extension of the crankcase of the engine a pipe 8 extends across the front of the engine to a point in the body of the carburetter 2. At an intermediate point in the pipe there is a flame-trap 9, comprising simply a casing containing a baie of metal gauze to eliminate the possibility of any flame, that might arise in the induction system through a fault, reaching the crankcase.

Referring now to FIGURES 2, 3 and 4 the carburetter 2 is of a well-known commercially available type in which an air valve member 10 is vertically movable, carrying with it a tapered needle valve 10A controlling the flow of fuel into the venturi formed by the space under the member 10. The member 10 is shown in its lowest position, and it is lifted by the action of a piston 11 of which the underside is exposed to the atmospheric pressure or to the pressure prevailing in the intake side 12 of the carburetter whilst the upper surface is exposed through a passage 12A to the pressure prevailing downstream (to the right in FIGURE 3) of the venturi.

Also mounted in the carburetter body, a short way downstream of the air valve member 10, is the throttle valve 13 in the form of a diametrally pivoted buttery valve.

The pipe 8 communicates with the space in the carburetter body between the air valve member 10 and the throttle valve 13 through a short tube 14 received in a drilled boss 15 formed in the body. In the example shown the tube 14 enters the body above the level of its axis and at a downwardly inclined angle of about forty-five degrees to the horizontal. Furthermore it will be noted that the tube is so placed that, as indicated in FIGURE 3, the edge of the throttle valve 13 passes over the end of the tube as the throttle is approaching its fully open position.

The optimum position for the tube 14 is best found by experiment for each individual engine, carburetter and induction manifold combination. We prefer to mount the tube above the level of the centre of the induction tract in order to reduce the possibility of liquid fuel that lies in the bottom of the tract finding its way into the tube. On the other hand, with six-cylinder engines we have found that position illustrated, which is asymmetric with respect to the throttle valve 13, can upset the distribution of the fuel-air charge lbetween the cylinders, and it is preferred in that case for the tube to open into the induction tract at a point on its vertical plane of symmetry. This can be done by bringing in the tube horizontally to break tangentially into the induction tract at its lowermost point. To prevent liquid fuel passing along the tube, the tube can be inclined slightly downwards towards the carburetter.

Although a carburetter with a sliding piston has been illustrated, it will be `appreciated that the invention may be applied to any other carburetter of the so-called constant vacuum or constant depression type, for example, to that type in which the movement of a variable air valve member is angular rather than linear and/or is controlled by a diaphragm rather than a piston.

We will now refer briey to FIGURE 5, which shows the arrangement used in the example under consideration at the crankcase end of the pipe 8 to reduce or eliminate the likelihood of oil from the crank-case being sucked up the pipe 8. The pipe 8 is fitted over a spigot member 16 which is mounted in a disc 17 that is pushed into an opening in the front wall of the crankcase extension and the inner end of the member 18, which is bell-mouthed, lies opposite the end of a shaft (not shown) that lies within the crankcase and is used to drive auxiliary components of the engine. A cup-shaped pressing 18 is secured on the end of the shaft by a nut 19 that holds a chain sprocket 20 on the shaft and this pressing 18, rotating with the shaft, acts as an oil slinger to throw clear any oil that approaches the region of the intake end of the spigot member 16, thus ensuring that only substantially oil-free air is drawn up the pipe 8.

It will be understood that the pipe 8 need not necessarily be connected to the cranlccase itself or even to an extension of it, but it could be connected to any part of the interior of the engine from which fumes are to .be withdrawn.

I claim:

1. In combination, an internal combustion engine, an induction system feeding said engine, a carburetter of the yconstant-depression type `connected to said induction system, a variable air valve in said carburetter, a throttle valve disposed between said air valve and said induction system, and a -breather pipe, one end of said pipe communicating with the interior of said engine and the other end of said pipe `communicating with the interior of said carburetter at a point between said air Valve and said throttle valve.

2. In combination, an internal-combustion engine having a crankcase, an induction system feeding said engine, a carburetter of the constant-depression type connected to said induction system, a variable air valve in said carburetter, a throttle valve disposed between said air Valve and said induction system, and a breather pipe, one end of said pipe communicating with the erankcase of said engine and the other end of said pipe communicating with the interior of said carburetter at a point between said air valve and said throttle valve.

3. In combination, an internal combustion engine having a crankcase, an induction system defining a pasage between atmosphere and the intake of said engine, a carburetter of the constant depression type comprising a variable air valve disposed in said passage, a throttle valve in said passage between said air valve and said engine, and a pipe forming a communication between the crankcase of said engine and a point in said passage between said air Valve and said throttle Valve.

4. The combination set forth in claim 3 comprising in addition a rotatable oil slinger, said oil slinger being disposed within said crankcase and adapted to rotate about an axis on operation of the engine, said pipe being in communcation with said crankcase at a point adjacent to and on the axis of said slinger.

5. The combination set forth in claim 3 comprising in 4addition a flame trap at an intermediate point in said pipe.

6. The combination set forth in claim 3 wherein said point of communication of said pipe with said passage is adjacent said throttle valve and wherein said throttle valve is yadapted for angular movement to an extent such that in substantially the fully open position thereof said Valve overlies said point of communication.

References Cited by the Examiner UNITED STATES PATENTS 1,305,036 5/1919 Vincent.

1,654,147 12/1927 Shannon 123-119 2,363,223 11/ 1944 Bonmier 261-44 X 2,737,935 3/1956 Olson 123-119 2,906,252 9/ 1959 Beardsley 123-119 3,111,120 11/1963 Cornell 123-119 3,116,727 1/1964 Dietrich 123-119 3,147,320 9/1964 Tubb 261-44 X 3,167,060 1/1965 Fowler 123--119 FOREIGN PATENTS 1,299,060 6/ 1962 France.

1,097,755 1/ 1961 Germany.

MARK NEWMAN, Primary Examiner.

KARL I. ALBRECHT, Examiner.

A. L. SMITH, Assistant Examiner. 

1. IN COMBINATON, AN INTERNAL COMBUSTION ENGINE, AN INDUCTION SYSTEM FEEDING SAID ENGINE, A CARBURETTER OF THE CONSTANT-DEPRESSION TYPE CONNECTED TO SAID INDUCTION SYSTEM, A VARIABLE AIR VALVE IN SAID CARBURETTER, A THROTTLE VALVE DISPOSED BETWEEN SAID AIR VALVE AND SAID INDUCTION SYSTEM, AND A BREATHER PIPE, ONE END OF SAID PIPE COMMUNICATING WITH THE INTERIOR OF SAID ENGINE AND THE OTHER END OF SAID PIPE COMMUNICATING WITH THE INTERIOR OF SAID CARBURETTER AT A POINT BETWEEN SAID AIR VALVE AND SAID THROTTLE VALVE. 